The White House says President Barack Obama is considering providing Syrian rebels with "non-lethal" aid in their year-long uprising against the country's autocratic leader Bashar al-Assad.

Obama discussed ways of helping the Syrian rebels with Turkish Prime Minister Recep Tayyip Erdogan on Sunday in Seoul, where they will attend a nuclear security summit. Deputy U.S. National Security Advisor Ben Rhodes says the two leaders agreed to raise the issue of non-lethal aid at a "Friends of Syria" meeting in Turkey on April 1. Rhodes says such aid may include medical supplies and communications equipment but not weapons.

After meeting Mr. Obama in Seoul, Erdogan said Turkey and its partners "cannot remain a spectator" to Syria's conflict and must do something "in the framework of international law." Obama said he and Mr. Erdogan also agreed that Syria must begin a transition to legitimate government.

The United States, Turkey and their allies have been reluctant to arm the loosely-organized Syrian rebels trying to oust President Assad, fearing that an escalation of the conflict will worsen a humanitarian crisis in parts of the country.

Russian President Dmitry Medvedev said Sunday a Syria peace plan drafted by international envoy Kofi Annan "may be the last chance" for the country to avoid a "protracted bloody civil war." Medvedev discussed the plan with Annan in Moscow on Sunday and promised assist him "at any level."

The U.N.-Arab League envoy's proposal calls on the Assad government and the rebels to agree to a cease-fire and begin a dialogue on resolving the conflict peacefully. After meeting the Russian president, Annan said the Assad government "has an opportunity" to work with him to end the fighting, allow humanitarian access to affected civilians and embark on a political process.

Syrian rights activists say pro-Assad troops continued assaults on several opposition hubs around the country on Sunday, shelling the central city of Homs and attacking rebels in the southern province of Daraa. They say several soldiers and rebels were killed in the fighting in the Daraa town of Nawa. Activists say Syrian rebels also attacked security forces near Damascus.

U.S.-based rights group Human Rights Watch accused the Syrian military of using civilians - including children and the elderly - as human shields in battles with the rebels. In a report released Sunday, the group said it had witness testimony of Syrian troops forcing civilians to march in front of government tanks in towns and villages in the northern province of Idlib.

Human Rights Watch called the use of human shields "abhorrent" and demanded that Syria immediately stop the practice.

The United Nations says at least 8,000 people have been killed in the Assad government's crackdown on the revolt, which began one year ago with peaceful protests, then became increasingly militarized.